For the second consecutive round of testing, students in Shanghai dramatically outscored the rest of the world on the Program for International Student Assessment (PISA), a global test of math, science, and reading skills for high schoolers.

They scored the equivalent of almost three years of schooling over most other countries assessed. As impressive as those numbers are, they are certainly not representative of the country as a whole.

"The Shanghai scores frankly to me are difficult to interpret," Brookings Institution senior fellow Tom Loveless told the AP. "They are almost meaningless."

There are a few reasons that comparing other countries with Shanghai simply doesn't work, and that any headline discussing "China's" PISA scores should be ignored.

The teachers there are paid more than double what those in outlying provinces make, and schools are significantly better funded.

Shanghai's per capita GDP is more than double the national average, and parents spend large sums on outside tutoring.

About 84% of Shanghai high school graduates go to college, according to Brookings, compared to 24% nationally. That means they pass China's extremely tough college entrance exam.

Test scores are emphasized as important and a source of national pride, significantly motivating students and teachers to perform.

Still, the scores represent an impressive level of performance, even if it is limited to one city. There's no denying that East Asian economies perform better overall, the top-seven math scores come from countries or cities in the region.

All of China is expected to be included in the 2015 assessment according to CNN, so we'll know how much of an outlier Shanghai is then.